1. Field of the Invention
The present invention relates to an optical disk recording apparatus and an optical disk recording method for recording information on a multilayer rewritable or write-once read-many optical disk. Further, the present invention relates to an optical disk reproducing apparatus for reproducing information from a multilayer rewritable or write-once read-many optical disk. Moreover, the present invention relates to improvement of a multilayer rewritable or write-once read-many optical disk.
2. Description of the Related Art
In recent years, it is widely known that a multilayer-type optical disk is developed for increasing the capacity of optical disks as information recording media. The multilayer optical disk makes it possible to selectively record or reproduce information on a plurality of layers by irradiating a recording or reproduction laser beam from either side of the disk.
Inside the optical disk, the laser beam passes through layers sequentially from a layer nearer to the irradiating side to a layer farther therefrom, reaches a target layer, and is converged thereon. In this manner, it is possible to write or read information from an intended layer of the optical disk.
During transmission through layers of the optical disk, however, the laser beam is deteriorated due to undesired reflection on respective layers. At this time, the light reflectance depends on whether information is recorded (recorded state) or not (unrecorded state) on a layer which the laser beam passes through.
Namely, it is impossible to record or reproduce information with the same characteristic depending on whether the laser beam passes through an unrecorded layer or a recorded layer to reach a farther layer for recording or reproducing information therefrom.
The same layer may contain unrecorded and recorded areas mixedly. When the laser beam passes through a boundary between the unrecorded and recorded areas, it is subject to an interlayer crosstalk due to a difference between light reflectances of both areas. This prevents desirable recording or reproduction on a layer farther therefrom.
Especially, some optical disks record the information for managing recorded information on a predetermined management information recording area. Such optical disks cannot maintain stable reliability of the management information to be recorded or reproduced depending on whether the management information recording area is preceded by an unrecorded or recorded layer.